Random impedance testing circuit and method for vector network analyzer material testing

The invention provides a random impedance testing circuit. The random impedance testing circuit comprises a frequency reference, a single-frequency signal source S1, a local oscillator L0, a coupling link module, a receiver A, a receiver B, a computer module and a impedance matching module; the receiver A and the receiver B each comprise an intermediate frequency conditioning module, an AD sampling module and a DSP module; the impedance matching module comprises a power divider, an adjustable attenuator, an adjustable phase shifter and a differential amplifier. By means of the random impedance testing circuit, a vector network analyzer can be tuned to be at any impedance, and the sensitivity of a system for conducting material testing is strengthened; compared with an impedance transition clamp with the conversional method, complex clamps do not need to be designed, time and labor are saved, and the matching accuracy is high.